// Copyright 2019 Yunion
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package cache

import (
	"fmt"

	"yunion.io/x/pkg/util/sets"
)

// Indexer is a storage interface that lets you list objects using multiple indexing functions
type Indexer interface {
	Store
	// Retrieve list of objects that match on the named indexing function
	Index(indexName string, obj interface{}) ([]interface{}, error)
	// IndexKeys returns the set of keys that match on the named indexing function.
	IndexKeys(indexName, indexKey string) ([]string, error)
	// ListIndexFuncValues returns the list of generated values of an Index func
	ListIndexFuncValues(indexName string) []string
	// ByIndex lists object that match on the named indexing function with the exact key
	ByIndex(indexName, indexKey string) ([]interface{}, error)
	// GetIndexer return the indexers
	GetIndexers() Indexers

	// AddIndexers adds more indexers to this store.  If you call this after you already have data
	// in the store, the results are undefined.
	AddIndexers(newIndexers Indexers) error
}

// IndexFunc knows how to provide an indexed value for an object.
type IndexFunc func(obj interface{}) ([]string, error)

// IndexFuncToKeyFuncAdapter adapts an indexFunc to a keyFunc.  This is only useful if your index function returns
// unique values for every object.  This is conversion can create errors when more than one key is found.  You
// should prefer to make proper key and index functions.
func IndexFuncToKeyFuncAdapter(indexFunc IndexFunc) KeyFunc {
	return func(obj interface{}) (string, error) {
		indexKeys, err := indexFunc(obj)
		if err != nil {
			return "", err
		}
		if len(indexKeys) > 1 {
			return "", fmt.Errorf("too many keys: %v", indexKeys)
		}
		if len(indexKeys) == 0 {
			return "", fmt.Errorf("unexpected empty indexKeys")
		}
		return indexKeys[0], nil
	}
}

// Index maps the indexed value to a set of keys in the store that match on that value
type Index map[string]sets.String

// Indexers maps a name to a IndexFunc
type Indexers map[string]IndexFunc

// Indices maps a name to an Index
type Indices map[string]Index